Determinants of coronary flow and myocardial metabolism in the newborn lamb. Influences of hypoxia and acidosis.

Abstract

Coronary blood flow and myocardial metabolism are subjects which have received intensive investigative interest since early in the present century (1). This work has been confined largely to the adults of many species, including man, while scant attention has been given to these problems in the newborn. In the early neonatal period there are major changes in cardiac output (2), in the distribution of blood flow (3) and in pressure relations within the various vascular compartments (4) associated with the transition to extrauterine life. Some of these changes may be reflected in the heart by a revision in the ratio of right to left ventricular weight from near unity at birth to one in which the left ventricle may weigh more than twice as much as the right at two to four weeks of age. Active myocardial growth is reflected in a remarkable increase in RNA synthetic processes which are most pronounced in the left ventricular myocardium (5).